UNIVERSITY    OF    CALIFORNIA  agricultural  Experiment  Station 

College  of  agriculture  e-  j-  wickson,  director 

BERKELEY,    CALIFORNIA 

CIRCULAR  No.  72 

(October,  1911) 


SALT  IN    CYANIDS 

GEO.  E.  COLBY  AND  GEO.  P.  GRAY. 


A  recent  publication  of  the  United  States  Department  of  Agri- 
culture1 has  shown  that  under  certain  conditions  the  presence  of 
common  salt  in  commercial  cyanids  produces  a  decomposition  of  the 
hydrocyanic  acid  gas.  Since  there  is  a  large  amount  of  cyanid  now 
being  used  for  fumigation  showing  chlorids  equivalent  to  over  18  per 
cent  sodium  chlorid  (common  salt),  which  according  to  the  above 
mentioned  tests  would  decrease  the  efficiency  one-third,  requiring  the 
use  of  one-half  more  cyanid  to  produce  the  same  amount  of  hydro- 
cyanic acid  gas,  the  Insecticide  Laboratory  undertook  a  special  study 
of  the  subject,  which  will  be  reported  in  detail  in  a  later  publication. 

The  purpose  of  the  present  preliminary  statement  is  to  furnish  the 
users  of  this  grade  of  cyanid  the  practical  results  of  this  work. 

The  tests  referred  to  above  were  made  with  a  solution  of  the 
cyanid, — one  part  in  two  parts  water  added  to  two  parts  acid  and  two 
parts  water,  and  this  method  will  here  be  called  the  "wet"  process. 
The  results  for  amounts  of  decomposed  hydrocyanic  acid  obtained 
upon  treating  cyanids  by  this  method  are  entirely  different  when  the 
"dry"  process  of  using  the  cyanid  is  employed,  approximating  closely 
the  method  universally  employed  in  actual  fumigation  work.  In  this 
method  one  part  of  dry  cyanid  is  throv/n  into  a  mixture  of  one  part 
acid  and  three  parts  water. 

When  fumigation  was  first  developed  by  this  station  the  production 
of  ammonia  gas  by  the  decomposition  of  the  hydrocyanic  acid  gas 
was  studied,2  and  the  substitution  of  the  "dry"  method  of  generating 
was  chiefly  to  avoid  the  injury  to  the  foliage  due  to  the  ammonia. 

The  apparatus  used  in  the  "dry"  process  in  this  laboratory  work 
was  similar  to  that  employed  by  the  Government  chemist:  the  tube 
into  the  generating  flask  simply  had  a  foot  bent  at  the  lower  end  upon 
Avhich  a  weighing  bottle  containing  the  weighed  cyanid  rested;  this 
was  introduced  into  the  flask  and  when  ready  a  twist  of  the  tube 
upset  the  cyanid  into  the  mixture  of  acid  and  water  just  below.  This 
is  practicnllv  what  is  done  in  fumigation  work  when  the  dry  cyanid 
is  dropped  into  the  acid  in  the  generator. 


i  Bureau  of  Entomology,  Bulletin  No    90,  Part  TTT. 

2  Calif ornia  Station  Bulletin  No.  79.    (See  also  Bulletin   No.  12!!.) 


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Sample  805  showed  by  the  "wet"  process  a  decomposition  of 
hydrocyanic  gas  varying  from  8.88  per  cent  to  16.88  per  cent;  the 
"dry"  test  on  this  sample  showed  a  decomposition  of  the  gas  from 
0.7  per  cent  to  2.86  per  cent,  and  another  sample,  806,  containing  a 
large  quantity  of  sodium  chlorid,  showed  a  very  large  percentage  of 
decomposed  cyanhydric  gas  by  the  "wet"  process. 

Two  other  samples,  Nos.  807  and  808,  showed  a  somewhat  higher 
decomposition  by  the  "dry"  method  than  No.  805,  but  still  the  results 
are  very  much  less  than  in  the  tests  made  by  the  "wet"  method. 

It  will  be  noted  that  the  powdered  cyanid  (No.  805)  when  treated 
by  the  "dry"  process  showed  considerably  greater  amounts  of  decom- 
posed cyanhydric  gas  than  when  the  materials  were  used  in  lumps, 
indicating  a  slight  action  in  the  direction  that  results  by  testing  the 
cyanid  in  solution. 

The  users  of  cyanid  should  appreciate  that  when  they  are  operating 
with  cyanids  rich  in  common  salt  they  are  sure  to  get  decomposition 
of  the  gas  if  they  use  the  finer  cyanid  in  the  bottom  of  the  case.  It 
is  probably  also  wise  to  take  care  that  the  cyanid  does  not  become  wet 
by  exposure  to  the  air. 

The  practical  conclusions  are: 

First — Where  there  are  no  chlorids  present  the  total  available 
cyanogen  is  nearly  all  converted  into  hydrocyanic  acid  gas. 

Second — When  chlorids  are  present  and  the  gas  is  generated  from 
solid  lumps  a  very  small  amount  pf  decomposition  occurs. 

Third — Cyanid  in  solution  suffers  very  great  decomposition  during 
generation  when  chlorids  are  present. 

Fourth — The  commercial  cyanids  now  being  used  are  good  for 
fumigation  purposes  even  if  they  contain  the  largest  amount  of  com- 
mon salt  yet  found,  provided  the  hydrocyanic  acid  gas  is  generated 
by  the  method  usually  followed  in  practice. 


